Swords & Wizardry is one of the premier retroclones of the OSR. It is based on the Original D&D and some of its supplements. It is such flexible platform, particularly S&W White Box, that gamers began to modify it and produce their own versions of S&W almost right away. This is intended to be a list of Swords & Wizardry games and their offspring. First are the three versions of Swords & Wizardry and then, in no particular order, the descendants.

Written by James Spahn. It is essentially his tweaked and expanded version of S&W White Box that gives the game a more heroic focus. And it includes 14(!) classes compared to the original 3 in White Box. A personal favorite of mine at the moment. Oh, and like several other items on this list, the PDF is free.

And look at that cover. Another one I like. Very evocative for me as it reminds me of my favorite cover for The Hobbit.Note: This appears to no longer be free.